1. Field of the Invention
The present invention relates to a planar light source and a backlight unit having the same, and more particularly, to a planar light source in which a layout structure of light emitting modules are optimized.
2. Description of the Related Art
In general, a cold cathode fluorescent lamp (CCFL) used as a light source of a backlight unit for a liquid crystal display (LCD) uses mercury gas. The mercury gas may cause the environmental contamination. In addition, the CCFL has slow response time and low color reproducibility. The CCFL is not appropriate for reducing the weight, thickness, length, and size of an LCD panel. Unlike the CCFL, a light emitting diode (LED) is environmentally friendly. In addition, the LED has a fast response time of about several nano seconds, thereby being effective for a video signal stream and enabling impulsive driving. Further, the LED has a color reproducibility of 100% or more and properly alters luminance, a color temperature, and the like by adjusting an amount of light emitted from red, green, and blue LEDs. Furthermore, the LED has advantages of reducing the weight, thickness, length, and size of the LCD panel. Therefore, in recent years, the LED has been widely used as the light source of the backlight unit for the LCD panel.
The backlight units employing the LEDs are classified in accordance with a location of the light source into edge-type backlight units and direct-type backlight units. The edge-type backlight unit is deigned such that a bar-type light source is located at a side to emit the light to an entire surface of the LCD panel using a light guide plate. The direct-type backlight unit is designed such that a planar light source having a substantially same surface area as the LCD panel is located under the LCD panel to directly emit the light to the entire surface of the LCD panel.
FIGS. 1 and 2 are top plane views illustrating a layout structure of light emitting modules of a planar light source according to a related art. As shown in FIG. 1, a planar light source 100 used for an LCD panel of the related art LCD panel includes a substrate 101 and a plurality of LEDs 103 that are arrayed on the substrate 101 in rows and columns. In this case, a plurality of bar-type light emitting modules each having the plurality of the LEDs 103 are properly interconnected and arrayed at left and right sides in the vertical direction. This light emitting module layout structure has limitations that connectors 104 for electrically interconnecting light emitting modules 102 must be disposed on left and right ends of each of the light emitting modules 102 and a large number of the light emitting modules 102 are required to reduce a thickness of a device and improve luminance uniformity.
In order to attenuate the limitations, a layout structure illustrated in FIG. 2 may be utilized. Referring to FIG. 2, a planar light source 200 of a related art includes a plurality of light emitting modules 201a, 201b, 201c, 201d, 201e, 202f, 201g, and 201h. Each of the light emitting modules 201a, 201b, 201c, 201d, 201e, 202f, 201g, and 201h includes a plurality of LEDs 203 that are two-dimensionally arranged in rows and columns and a connector 204a (204b, 204c, 204d, 204e, 204f, 204g, 204h). The numbers of the light emitting modules and connectors in the layout structure of FIG. 2 may less than the numbers of the light emitting modules and connectors in the layout structure of FIG. 1. However, when only one kind of the LED modules 201a is used to improve the efficiency, as shown in FIG. 2, the connectors 204a, 204b, 204c, 204d, 204e, 204f, 204g, and 204h are linearly arrayed at left and right sides or inner sides and thus the electric wiring structure is not efficient.
Therefore, there is a need for a scheme that can optimize a layout structure of the light emitting modules of the planar light source.